Large Scale Central

Back to the drawing board

Track and Trestles
#1

I had what I thought was a really good idea, but it didn’t pan out at all. I’m currently making foundations for the bents on a trestle, casting them in place using forms made of foamcore. Until now, I’ve just been spooning a mix of mortar and vinyl patcher into the forms, but it’s messy. So I bought some pvc pipes, a brass nipple and a short piece of thin hose and built myself kind of a mortar injector. Basically like a really big hypodermic needle. Figured I could just put the end of the tube into the form and pump it full.

Well, unfortunately it doesn’t work at all. Trying to push the mortar through the tube, it just packs down and doesn’t move, no matter how thin I mix it.

#2

maybe you need more fiber in your diet…sorry I couldn’t resist!

cale

#3

Well if you got a concrete pump that can push the stuff at a couple hundred PSI, ya might have something, otherwise stick to the low tech trowel…:smiley:

#4

Ray,

Try using a dowel to push the concrete through the pcv pipe which should push it out the hose. If this dosen’t work you could borrow your wifes cookie press.

chuckger

#5

The real concrete pump trucks use some sort of Archimedes Screw, not a plunger. I think thats a bit of over-engineering for our modeling purposes, but its interesting to see how they solved the same problem.

#6
Charles Cole said:
Try using a dowel to push the concrete through the pcv pipe which should push it out the hose.
That's what I was doing. It just compacts instead of flowing.
#7

how about just making a large funnel, take a bleach bottle or a 2l coke bottle cut off the bottom, with cap on mix in container, the take the cap off and let it drain where you need it? If it doesnt pour fast enough cut back on the opening till it works

#8

Would covering the tube with something like pam work? sounds like the mix is sticking to the tube.

#9

They make a grout bag ( looks like a cake decorator’s bag)

(http://images.orgill.com/200x200/1940592.jpg)

Go to HardwareStore.com May be this will help!

#10

Thanks for all the suggestions. The grout bag is an idea I’d wondered about before hand but never knew such a thing existed. Might be the way to go if all else fails. The funnel seems like it would work, if I can find one that can have a small flexible tube attached to get past tight clearances. I know this mortar mix leaks out of small holes in the forms easy enough, so a funnel ought to work.

I did manage to finish the foundations for all the bents on this current trestle, just spooning the mortar in. So the trestle will be finished soon. It’s about five feet long, and curved. This is for the outer curve of track on the double track horseshoe curve at the lower east end of the layout. Next will be finishing up the two small trestles for the inner track, and then building and installing the bents for the big ten-foot long trestle.

#11

Although it sounds (and looks) like you might have solved your concrete placement issue. For the future I might make some suggetions. Having been in the concrete supply business for over 30 years, I have actually retained some knowledge… (my Wife might argue that).

What you might consider is the addition of a “Water Reducing Admixture” to the mix. This is normally in liquid form, and just a very small amount added to your mix will ‘wet’ your concrete an amazing amount. It is not really wet, but the surfce tension of the water has been broken down, and the mixture will ‘flow’ like crazy. You might even find that it will pour through a reasonably small tubing in order to get it where you want it. Reasonable means probably no smaller than 1.5 inches, maybe larger.

Stop by your local Ready Mixed Concrete plant, and sweet talk the batchman or plant manager for a sample quantity of water reducer. Two to Three ounces in a full 1 sack mixer of concrete will be sufficient. If you are mixing small amounts in a bucket or wheelbarrow, measure by the tablespoon… this stuff is pretty drastic.

Not only will it help in placement, you will find that the finished concrete will be nearly perfect, and most if not all, of the bubbles normally trapped in your forms will be gone. Even though the concrete looks ‘wetter’, it is really not wetter, just more fluid. The setting time is almost normal, and the best part is the strength will be improved. Ask the guys for a normal set water reducer, and if they can be talked out of a gallon (bring a jug), you will be set for a LONG time. The stuff is safe, non staining, and easy to use. (for what it is worth, they make a retarded set version too, which gives you an extended set time… gives you an hour or so longer before initial set.) Good Luck.